1. Field of the Invention
The present general inventive concept generally relates to a method and an apparatus to control operation of an equalizer such that a configuration of the equalizer can be easily implemented in hardware by adaptively selecting and updating one or more tap coefficients of the equalizer without separately estimating channel information.
2. Description of the Related Art
In a digital communication channel, unwanted intersymbol interference (ISI) is generated in an amplitude and a phase of a signal that is transmitted along the digital communication channel due to abnormal characteristics in a limited bandwidth. The intersymbol interference becomes a major obstacle to efficient usage of a frequency band and performance improvement. In order to compensate the signal that is distorted by the intersymbol interference, an equalizer becomes necessary. The equalizer may be necessary with a digital broadcast as well as with an analog broadcast.
A VSB (Vestigial sideband) modulation or a COFDM (Coded Orthogonal Frequency Division Mutiplexing) modulation may be used to transmit signals in the digital broadcast.
A data frame transmitted by the digital broadcast of the VSB modulation includes two data fields, each data field including 313 data segments. Out of these 313 data segments, a first data segment is a synchronizing signal and includes a training data string (hereinafter ‘training string signal’) used by the equalizer in a receiver. Additionally, TDS-OFDM (time domain synchronous-OFDM), which is a type of OFDM (orthogonal frequency division multiplexing), transfers an OFDM frame signal formed by interposing the training string signal.
The training string signal is a signal that is previously set between a receiving side and a transmitting side, and provides information for correcting channel distortion. The channel distortion refers to a phenomenon in which a radio wave that carries the digital communication channel is transformed into a form other than an original form due to various occurrences during transmission of the radio wave. The equalizer can select proper tap coefficients using the training string signal.
Some equalizers have attempted to equalize the digital communication channel by selecting and/or updating a proper tap coefficient according to a channel environment thereof. These equalizers have been able to reduce noise and obtain a rapidly converging error by enlarging the step size, as opposed to an equalization process that is performed using all of the taps of the equalizer. Thus, technology that estimates channels using various methods have recently been developed. By using estimated channel information, a tap to be used during equalization can be selected and updated.
However, when the tap and a corresponding coefficient are selected according to an incorrect estimation of the channel information, the performance of the equalizer may deteriorate. Thus, complicated algorithms are typically utilized to estimate the channel information. Accordingly, hardware used to implement the complicated algorithms has become increasingly complicated.